The filing deadline for 2016 tax returns lands midnight Tuesday. While no post offices will be open until midnight, the Santa Ana processing center will be, according to the postal service. That address is 3101 Sunflower Ave.

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Liz Estrada, office manager of H&R Block in Riverside, said her office will be open on Easter as well as extending hours on Tuesday. The staff will be busy but will take walk-ins and drop-offs, she said in an email.

Nearly one in three taxpayers wait until April to file, according to Kathy Pickering, executive vice president of The Tax Institute at H&R Block.

Fees are steep for not filing on time. The monthly penalty for not filing a tax return is 10 times greater than the penalty for not paying in full, she said in a news release, and could add up to 25 percent to a tax bill.

The days of people rushing to the post office on Tax Day are a distant memory. This year, the Internal Revenue Service projects more than 80 percent of taxpayers will use e-file, either through professional tax preparers or on their own.

As of April 7, the IRS recorded 103,612,000 individual returns; 95,458,000 were e-filing receipts.

Most post offices won’t have extended hours on Tuesday. In the Inland Empire, the U.S. Postal Service processing and distribution center at 1900 Redlands Boulevard, San Bernardino, will collect mail until 8 p.m.

The reason for late mail collection, of course, is to get a postmark of April 18, 2017 on the envelope, thus avoiding a late fee.

E-filers also need a timely postmark, but it is an electronic time stamp. To avoid computer crashes or glitches, taxpayers shouldn’t wait until 11:59 p.m. to hit the send button in Turbo Tax or other online services.

To help you get motivated, here’s a filing cheat sheet:

Extensions

If you are unable to make the April 18 deadline, you can request an extension.

To avoid a late payment penalty, you still need to estimate the amount owed and pay it while filing your taxes later.

Earned income tax credit

The California earned income tax credit is entering its second year. The credit applies to people who earn $6,717 or less with no children up to $14,161 with two or more children.

Watch out for scams

The IRS will not ask for your credit card or send the sheriff to your house. Anyone threatening to do so over the phone is likely a scammer.

Anyone impersonating the IRS can be reported online at ftccomplaintassistant.gov or by calling 800-366-4484.

Paper: Your paper return is filed on time if it is mailed in an envelope that is properly addressed, has enough postage, and is postmarked by the due date.

Registered mail: If you send your return by registered mail, the date of the registration is the postmark date. The registration is evidence that the return was delivered.

Certified mail: If you send a return by certified mail and have your receipt postmarked by a postal employee, the date on the receipt is the postmark date. The postmarked certified mail receipt is evidence that the return was delivered.

IRS e-file: Your return is considered filed on time if the authorized electronic return transmitter postmarks the transmission by the due date. An authorized electronic return transmitter is a participant in the IRS e-file program that transmits electronic tax return information directly to the IRS.

Electronic postmark: It is a record of when the authorized electronic return transmitter received the transmission of your electronically filed return on its host system. The date and time in your time zone controls whether your electronically filed return is timely.

Fielding Buck has been a business reporter since 2014 with a focus on logistics, supply chain and GIS. Prior experience includes extensive entertainment reporting. He loves photography and dogs and lives in San Bernardino County.